Cifregen1

#include <iostream>

using namespace std;
/**
1. Stiva de lungime n
2. Pe stiva punem litere consecutive ale alfabetului
3. Validare: v[1]=v[n]='a'
*/
char lit[]="abcdefghijklmopqrstuvwxyz";
int n,st[27];
void Afisare()
{
   for(int i=1;i<=n;i++)
        cout<<lit[st[i]];
   cout<<"\n";
}
int Modul(int x)
{
    if(x<0) x=-x;
    return x;
}
int Valid(int top)
{
   if(top==n-1 and st[top]!= 1) return 0;
   if(top==n and st[top]!=0) return 0;
   if(top>1 and Modul(st[top]-st[top-1])!=1) return 0;
   return 1;
}
void Back()
{
    int cand,top;
    top=1;
    st[top]=0;
    top=2;
    while(top>1)
    {
        cand=0;
        while(!cand and st[top]<25)
        {
            st[top]++;
            cand=Valid(top);
        }
        if(!cand) top--;
        else if(top==n) Afisare();
        else st[++top]=-1;
    }
}
int main()
{
    cin>>n;
    Back();
    return 0;
}